The present invention relates to a fastening system suitable for use on absorbent articles. More particularly, the present invention relates to absorbent articles having improved fit and stability of closure provided by the fastening system.
Absorbent articles such as diapers, training pants or incontinence garments desirably provide a close, comfortable fit about the wearer and contain body exudates. Disposable absorbent articles can be secured about the wearer by a variety of fastening systems. Conventional diapers have typically included a front waist portion and a back waist portion that are releasably connected about the hips of the wearer during use by conventional fastening systems such as adhesive tape fasteners or hook and loop fasteners. For example, conventional fastening systems typically include a pair of fasteners, such as hook tabs, located on the outermost corners of the diaper in the back waist region of the diaper and a complimentary fastener, such as a loop panel, located on the exterior surface of the outer cover of the diaper in the front waist portion of the diaper. Typically, when a user dons the article, the hook tabs and the back waist region are lapped over the front waist portion of the article and the hook tabs are secured to the loop panel. The overlapping front and rear waist regions are in surface-to-surface contact and create the waist opening. Because the waist opening is typically formed by the union of the front waist portion and the back waist portion, the fastening system used to form that union may impact the fit of the absorbent article.
Once the article is being worn, the quality of the fit at the waist opening is a primary driver of the fit of the whole article. Just like the elastic waistband of the cloth underwear, the fit of the waist opening keeps the absorbent article from falling down. If an absorbent article begins to droop or sag during wear, the performance of the article may be compromised. More specifically, the article may leak.
The performance and containment of the absorbent article is typically improved by providing tension around the waist opening of the article and also by providing tension around the leg openings of the absorbent article through the addition of extensible materials to the product. Such conventional diapers have tension around the waist of the user and tension around the leg of the user when initially donned. It is desirable for an absorbent article to maintain its initial fastened position during use so as to maintain proper tension and ultimately proper fit. It is also desirable for absorbent articles to resist radial shifting in the fastener overlap region in the front portion of article so as to maintain both the leg tension and the waist tension. In various types of garments, such as a disposable diaper, the secured together portions of the garment, particularly in the fastener overlap region, are placed under tension. The tension in the fastening system results primarily from shear forces, both from the material elasticity and from user movements. The shear forces act to pull the fastening system apart in a direction essentially planer to the interface between the back fastener and the front fastener. Therefore, improvements in shear strength can improve fastening performance and in turn improve fit by reducing slippage and radial shifting due to the shear forces in the fastener overlap region. However, increased shear strength can also result in increased peel strength. The peel strength is a measure of the force required to pull (or peel) the back fastener away from the front fastener in a non-parallel direction. This force is felt by the user when removing the back fasteners from the front fasteners. Excessive peel strength can result in user dissatisfaction due to fasteners that are difficult to open.
Traditional absorbent products have not been optimized to resist radial shifting and shear slippage while maintaining acceptable peel strengths. The front waist portion of an absorbent article is generally flexible for comfort and fit. Also, the materials that make up the front and rear waist portions of absorbent articles have relatively low coefficients of friction when in surface-to-surface contact with one another. The result in traditional absorbent articles is that the leg elastic tension may pull down the front waist portion of the article causing radial shifting of the front waist portion of the article with respect to the rear waist portion of the article in the overlap section or slippage due to shear forces. This shifting and slippage may result in an undesirable loss of tension in both the waist opening and the leg portions of the absorbent garment. The loss of tension may also lead to reduction in the containment and performance of the article. The radial shifting may be worsened when the user attaches the tabs near the center of the front waist portion of the article thus increasing the amount of overlap between the front and rear waist portions of the absorbent article.
There exists a need for a fastening system that can reliably maintain the proper relationship between the rear and front waist portions and thereby maintain proper fit and tension in absorbent articles during use. There is also a need for a fastening system that can reduce radial shifting and shear slippage between the back and front waist regions while maintaining desirable peel strength. There is also a need for a fastening system that is gentle to the skin and does not cause red marking or discomfort during use.